1. Field of the Invention
The present invention pertains to safety needle instruments and, more particularly, to safety needle instruments including needles having sharp tips for penetrating anatomical tissue to establish communication with anatomical cavities wherein tissue and organ structures are protected from the tips of the needles.
2. Discussion of the Prior Art
Penetrating instruments are widely used in medical procedures to gain access to anatomical cavities ranging in size from the abdomen to small blood vessels, such as veins and arteries, epidural, pleural and subarachnoid spaces, heart ventricles and spinal and synovial cavities. Such penetrating instruments typically include an outer sleeve or cannula and a penetrating member disposed within the cannula and having a sharp tip for penetrating an anatomical cavity wall with the force required to penetrate the cavity wall being dependent upon the type and thickness of the tissue forming the cavity wall. Once the wall is penetrated, it is desirable to protect the sharp tip of the penetrating member from inadvertent contact with or injury to tissue or organ structures in or forming the cavity in that, once penetration is achieved, the lack of tissue resistance can result in the sharp tip traveling too far into the cavity and injuring adjacent tissue or organ structures.
Various safety penetrating instruments have been proposed, generally falling into protruding and retracting categories. In protruding safety penetrating instruments, a safety member is spring-biased to protrude beyond the tip of the penetrating member in response to the reduced force on the distal end of the safety member upon entry into the anatomical cavity. Safety needle instruments including a safety member in the form of a probe biased to protrude beyond the sharp tip of a needle have become widely accepted for use in penetrating anatomical cavities. For example, the Verres needle, commonly used to create a pneumoperitoneum, has a spring-loaded inner member disposed within a tubular needle. Safety trocars having a safety member in the form of a spring-biased protective shield disposed between an outer sleeve and an inner trocar are also known.
Retractable safety penetrating instruments typically include a trocar disposed within a portal sleeve and retractable within the sleeve in response to distally-biased movement of a component of the safety penetrating instrument, such as the trocar or the sleeve, caused by a reduction in force from tissue contact upon entering the anatomical cavity.
One of the limitations of many prior art safety needle instruments is that the safety probes can produce an irregular surface or profile with the sharp tips of the needles during penetration of tissue resulting in increased resistance during penetration of an anatomical cavity wall, trauma and damage to tissue and possible jamming of trapping of tissue. Another limitation of many prior art safety needle instruments is that very small or narrow anatomical cavities cannot be penetrated without protrusion of the safety probes from the sharp tips of the needles. A further limitation of many prior art safety needle instruments is that the needles cannot be automatically retracted to safe, protected positions wherein the sharp tips of the needles are disposed within the instruments upon penetration into anatomical cavities.